High-frequency electromagnetic fields on perfectly conducting concave cylindrical surfaces

High-frequency fields are investigated on the surface of a perfectly conducting concave circular cylindrical segment excited by an arbitrarily oriented dipole located on the surface. The vector fields are derived from two scalar Green's functions which are constructed as contour integrals and evaluated asymptotically in two alternative ways. In one representation an appropriate number of geometrical optics rays is extracted to provide canonical remainder integrals with highly improved convergence characteristics. In the second approach a properly determined combination of rays together with
E
- and
H
-type whispering gallery modes is utilized. Numerical results are presented for the magnitude and polarization of the fields as functions of dipole orientation and observation point location, and are interpreted in terms of the physical models implied by the various field representations. As for scalar sources, the hybrid ray-mode formulation of vector-source excited fields provides a physically attractive and numerically efficient scheme.